Later, the use of antibody microarrays permitted the quantification of oxidative-stress-related proteins in 10 POAG and 10 control patients, showing lower SOD and glutathione transferase (GST), along with higher glutamine synthase (GS) and nitric oxide synthase (NOS), in the aqueous humor of glaucoma patients, leading to the hypothesis that the reduced expression of the antioxidant enzymes SOD and GST could aggravate the imbalance between the production and detoxification of oxygen- and nitrogen-derived free radicals [67]. Here, GLUL is linked to glaucoma.